There is known an inverter engine-driven power generator in which an output of an engine-driven power generator is rectified in a rectifying circuit and is converted into an AC output having a predetermined frequency in an inverter circuit to supply a power to a load. For example, Japanese Patent Application Laid-Open No. 2004-282827 discloses an inverter power generator in which a bidirectional DC/DC converter is provided between an output side of the rectifying circuit and an output terminal of a battery, and if the output of the rectifying circuit is lacking during an overload state, the lacking output from the rectifying circuit can be supplied from the battery.
Since the inverter power generator can change its frequency depending on the load, the engine is operated in the idle state while the load is absent, thereby enhancing low-fuel consumption and low-noise performance. However, it is desired that the engine is stopped when the load is absent to further enhance low-fuel consumption and low-noise performance. On the other hand, it is complicated for an operator of the load to stop the engine each time the load stops being driven, and thus there is desired a system capable of detecting the stop of the load and automatically stopping the engine particularly while the operator is operating or driving the load at a distant place from the power generator.
A means for detecting the presence of the load is required for automatically stopping the engine. There is proposed in Japanese Patent Publication No. 2882174 a start/stop control device for an engine-driven power generator in which when the engine frequency is less than a set value, a connection is switched from a load connection terminal to a load detection power supply circuit, when a load is connected to the load connection terminal, a current flows from the load detection power supply circuit to the load, and when the current is larger than the set value, the engine is started.